Internal brake



v Sept. 27, 1938. A T. cHAsE Er AL INTERNAL BRAKE Filed Nov. l25," 193s 2 sheets-sheer 2 Patented Sept. 27, 1938 Y UNITED STATES PATENT oFFicE INTERNAL BRAKE Theron P. Chase and George E. Martin, Detroit,

Mich., assignors, by mesne assignments, to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application November Z5, 1933, Serial No. 699,640

` 9 claims. (o1. 18s-7s) a r This invention relates to brakes and has been 45. Into each wall 45 is threaded a cup 41. The designed more particularly as an improvement in circumferential edge of the cup clamps the flange y a brake for use on vehicle wheels. 49 of a ilexible cup 5I of rubber or the like be- An object of the invention is to provide a brake tween itself and the oor 43. To reduce the cain which both shoes do an equal amount of work pacity of the chamber within the rubber cup and, therefore, have a lower maximumpressure there may be provided avblock 53 shouldered to per unit area than where one shoe is doing more seat on the edge of the floor 43 surrounding the than the other as in the two-shoe brake with sinspace 39. The block is secured by fastening means gle actuation means. y 40. This block is provided with a passage 55 afl0 A further object is to provide a brake having fording communication between space 39 and the 10 a plurality of shoes which are self-actuating for region beneath the rubber cup whereby fluid passeitherdirection of drum rotation. ing through passage 38 and space 39 may push A still further object is to provide an arrangeoutwardly on the rubber cup. The outward movement whereby the pressure of each shoe will balment of the rubber cup pushes a piston or plunger ance the pressure of the other and whereby the 51.' As shown at the upper left side of Fig. 1, this 15 l torque reaction on the supporting structure is piston 51 is guided by the inner wall of cup 41.

balanced. It also is guided by an opening in the otherwise Other objects and advantages wili be underciosed end of the cup 41. Axially slidable on the stood from the following description. outer wall of cup 41 is a cupped member 59 con- The invention may be embodied in a brake opstituting a part of a link 6I which is pivoted to 20 erated by any suitable hydraulic medium and also one of the brake shoes 54 at 55. Preferably at in a brake operated by mechanical linkage. the point of application of force to the other shoe, Fig. 1 shows partly in vertical section and partly adjustment is provided. To this end a yoke 63 is in elevation one embodiment of the invention. carried on a pin 65 at the end of shoe 54'. The

Fig. 2 is a section on line 2-2 of Fig. 1. yoke has a rounded surface 61 engaging between 25 Fig. 3 is a perspective of parts disassembled. walls '59 of a member 1I having a threaded stem Fig. 4 is a view partly in section and partly in 13. Stem 13 is threaded into an opening 15 of the elevation showing a modied form. extended end 11 of a cup-shaped member 59' slid- Fig. 5 is a view with parts broken away and in able along the outer wall of part 41. For turning section as seen from line 5-5 of Fig. 4. part 59 there is provided thereon a notched ring 3o Referring first to Fig. 1, numeral 9 is the rela- 18. The backing plate is shown in Fig. 2 as tively xed backing plate which is carried by the provided with an opening 19 over which is pivoted axle, not shown. The drum carried by the wheel a cover 8| which may be turned to give access is shown in section by numeral II. At diametrito the notched ring 18. It will be seen that by rocally opposite points are two anchor pins I3. Surtation of 59' the shoe end may be moved toward 35 rounding each anchor pin is a sleeve I5 having a or away from the drum surface. A spring 83 has shoulder I1. The pin I3 isY also shouldered at I9, end connections to the two shoe ends whereby the and a nut2I is threaded on its reduced end. members 59 and 59 are held against the members Around the 'sleeve I5 between the shoulder I1 and 41 when the hydraulic pressure is released. The

40 a spacer 23 is rotatably supported a double hyanchor pin I3 together with the parts 25 and 41 40 draulic wheel cylinder unit 25. This unit has thus becomes an anchor means for the shoes. bosses 21 projecting through openings 29 in the When the hydraulic pressure is applied the membacking plate. One of these bosses is shown by bers 51 are pushed outwardly, the applied force Fig. 2. The other boss is shown in dotted lines in tending to push the parts 59 and 59 outwardly Fig. 1. It iS above the DVO I3 and has an air and thus to force the ends of the shoes against the 45 bleed passage 28. A conduit 3l from a master drum. Precisely the same arrangement is made cylinder 0f an hydraulic system is connectedby use of at the other pair of adjacent shoe ends,

a T33 with conduits 35. The conduit 35 -for each each shoe having a long link 6I at its heel end unit 25 is connected by a suitable fitting 31 to an for checking forward travel.

opening in boss 21.` This opening communicates It will be seen that for forward travel as shown 50 by a passage 38 with an open space 39. The two by arrow A, shoe 54 is self-actuated by drum rospaces 39 of eacr .mit 25 are connected by a pas'- tation to an anchorage at its left end against its sage 4I. These spaces 39 are formed by removcooperating part 41 and pin I3. Its right end is ing material from below oors 43 formed on the applied by hydraulic power so that the shoe is unit 25 from which floors extend circular walls one having an articulated anchorage through the instrumentality of link 6|. Similarly shoe 54' anchors at its right end by means of link 6| on opposite pin I3. Hydraulic actuation at its left end makes it too a self-actuating shoe with articulated anchorage. When the shoes are so applied the unit 25 may tend to rotate slightly counterclockwise under the influence of relative` rotation between the parts at 55. The relative movement between parts 63 and 1| permits the necessary accommodation and provides that the applied force shall act substantially on a line through 3 and 65. In the case where the brake is applied to check reverse rotation of the drum and wheel, as shown by arrow B, the right end of shoe 54 and the left end of shoe 54' anchor, and the opposite ends are the applied ends. Here, too, both shoes lwill be seen to be self-actuated and to have an articulated link anchorage. A relatively large area of contact is provided by the two shoes. Since the two shoes are equally dimensioned and since both are similarly self-actuating there is no tendency to displace the drum as when one shoe operates 'with a force greater than the other. that of the other. Also, the components of the tangential forces acting through the linkage and which components tend to produce translation of the backing plate and axle are equal and opposite." 'I'he torque reaction may therefore be said to be`l balancedf In Fig. 4 and Fig. 5 the invention is shown applied to a mechanically-operated brake. Numerals 9 and represent the backing plate and drum as before. The shoes |0| and |03 are disposed in the same manner as are shoes 54 and 54' of the other form. At one end each shoe is provided with a pair of spaced extensions |05 having arcuatet ends engaging, when the brake is released, a-hollow cylindrical anchor |01 which has a'radially enlarged region |09 secured to the anchor plate by fastening means Between the adjacent extensions a ioller sector ||3 is pivoted as at H5. This sector projects through an opening ||1 in the wall of |01 to engage a cam ||9 located therein as shown by Fig. 4.- Another opening |2| in cylinder |01 receives another camengaging sector 3 pivoted to a block |25. This block has spaced extensions embracing the sector, the extensions having arcuate end faces desgned to engage the cylindrical anchor |01. Freely mounted within an opening in part |25 is a stem Its outer end is inv threaded engagement with a tubular link |29 pivoted to shoe |0| at |3|. Secured to block |25 is a yielding nnger |33 designed to adjustably engage the notched ring |35 carried by stem |21. By rotating ring |35 which is in abutment with block |25, the link |29 may be moved to provide a greater or lesser clearance between the end of shoe |0| and the drum. The cam ||9 is carried on a cam shaft |31, the outer end of which carries a spherical bearing |39 supported in the cup-shaped Vend of part |01 and a cap 4| threaded thereon. The shaft has an operating lever arm |43. The inner end of the shaft is given some degree of free movement as shown at |45 in Fig. 5. By this arrangement the cam may move to accommodate unequal shoe clearance and to insure an equal division of the applied force to the two shoes. A spring |41 is attached to the two shoes near theirends. 'Ihis spring holds the shoes in their released position with the arcuate ends seated on'the anchorage element |01. A duplicate construction is provided between the other pair of adjacent shoe ends.v The cam shaft arm |43 of the other cam I9 The pressure of each shoe will balance may be connected by a link |49 with arm |43 and Y an operating link |5| attached to arm |43 may be used for rotating the two cams simultaneously. It will be understood that link |5| is to be pulled by any suitable brake hook-up between itself and the pedal or other operating member. Here as before the symmetrical character of the shoes and their equal dimensions enable each to do an equal amountof work with the consequence of avoiding drum distortion. The forces applied by the two cams act tangentially and in opposite directions, constituting a couple acting on the anchor plate but having no tendency to cause translation of the axle which carries the plate. As in the case first described the forward rotation is checked by both shoes acting at their heel end with an articulated anchorage. In this form the reverse rolbetween each pair of adjacent ends of said shoes,

articulating links pivoted to symmetrically opposite ends of said shoes and engaging the adjacent anchor means, means whereby the other ends of said shoes may anchor directly on said anchoring means, movable means cooperating with a part of said anchor means to constitute applying means between both pairs of adjacent ends of the shoes whereby both shoes are selfactuating for either vdirection of drum rotation; whereby the pressure of the shoes is balanced; and whereby also the torque reaction on the supporting structure is balanced.

2. The invention dened by claim 1, said applying means including a floating cam to equalize the applied pressure between the two shoes.

3. The invention defined by claim 1, said anchor means consisting of tubular members secured to and extending through said anchor plate to rotatably engage said links at the adjacent ends of said shoes, said applying means comprising cam shafts universally mounted at the outer ends of said tubular member and provided with cams,

- said shoes having roller sectors extended through wheel brake unit pivoted on each of said anchor.

means, opposed pistons in said unit mounted ,to move on axes forming an obtuse angle with each other, and link means pivoted to the adjacent shoe ends and actuatedby said pistons.

, 6. The invention dened by claim 5, one of the links of each pair being mounted to slide axiallywith its actuating piston and the other having a rocking mounting relative thereto whereby an articulated anchorage is provided for both directions oi drum rotation. g

'7. 'I'he invention defined by claim 5, kone of said links of each pair`being mounted to slide axially with its actuating piston and the other comprising a plurality of parts constructed to provide axial adjustment and relative rocking.

8. In a brake, adrum, an anchor plate, two

equally dimensioned shoes, a single anchoring* means including as a part thereof an anchor'. pin

one such anchoring means being positionedfbe`A alarms tween each pair of adjacent ends of said shoes,

Varticulating links pivoted at points on symmetrically opposite ends of said shoes and engageable with said anchoring means, means whereby the other ends of said shoes may anchor directly on said anchoring means, movable means cooperating with a part of said anchor means to constitute applying means between both pairs of adjacent ends, said movable means including a member movable in an axis determined by said anchor pin and the pivot between the shoe and link whereby both shoes are self-actuating for either direction of drum rotation whereby the pressure of the shoes is balanced, and whereby also the torque reaction on the supporting struc-- ture is balanced.

9. A brake comprising a pair of iloating shoes, two anchors for the ends of the shoes on opposite sides of the brake, connected applying levers acting on the ends of the shoes on opposite sides of the brake and swinging in a plane paralleling the plane of the brake, and an adjustable partat one end of each shoe acting on the corresponding anchor and engaged by the corresponding lever, saldlparts serving to adjust the brake for wear without disturbing either the anchorage or the operation of the applying levers of the brake.

'nmaom P. CHASE. GEO. E. MARTIN. 

